More elegant way of solving #5839 (d_private in sceIoDread)

We flag filesystems as being FAT32 instead of checking for "ms0:".

Core/FileSystems/MetaFileSystem.cpp

@@ -255,6 +255,10 @@ std::string MetaFileSystem::NormalizePrefix(std::string prefix) const {
 	if (startsWith(prefix, "host"))
 		prefix = "host0:";
 
+	// Should we simply make this case insensitive?
+	if (prefix == "DISC0:")
+		prefix = "disc0:";
+
 	return prefix;
 }
 
@@ -284,6 +288,13 @@ void MetaFileSystem::Remount(IFileSystem *oldSystem, IFileSystem *newSystem) {
 	}
 }
 
+IFileSystem *MetaFileSystem::GetSystemFromFilename(const std::string &filename) {
+	size_t prefixPos = filename.find(':');
+	if (prefixPos == filename.npos)
+		return 0;
+	return GetSystem(filename.substr(0, prefixPos + 1));
+}
+
 IFileSystem *MetaFileSystem::GetSystem(const std::string &prefix) {
 	for (auto it = fileSystems.begin(); it != fileSystems.end(); ++it) {
 		if (it->prefix == NormalizePrefix(prefix))